Rushing to Judgment (Global Warming Questioned

Is Earth warming? The planet has warmed since the mid-1800s, but before that it cooled for more than five centuries. Cycles of warming and cooling have been part of Earth’s natural climate history for millions of years. So what is the global warming debate about? It’s about the proposition that human use of fossil fuels has contributed significantly to the past century’s warming, and that expected future warming may have catastrophic global consequences. But hard evidence for this human contribution simply does not exist; the evidence we have is suggestive at best. Does that mean the human effects are not occurring? Not necessarily. But media coverage of global warming has been so alarmist that it fails to convey how flimsy the evidence really is. Most people don’t realize that many strong statements about a human contribution to global warming are based more on politics than on science. Indeed, the climate change issue has become so highly politicized that its scientific and political aspects are now almost indistinguishable. The United Nations Intergovernmental Panel on Climate Change (IPCC), upon which governments everywhere have depended for the best scientific information, has been transformed from a bona fide effort in international scientific cooperation into what one of its leading participants terms “a hybrid scientific/political organization.”

Yet apart from the overheated politics, climate change remains a fascinating and important scientific subject. Climate dynamics and climate history are extraordinarily complex, and despite intensive study for decades, scientists are not yet able to explain satisfactorily such basic phenomena as extreme weather events (hurricanes, tornadoes, droughts), El Niño variations, historical climate cycles, and trends of atmospheric temperatures. The scientific uncertainties about all these matters are great, and not surprisingly, competent scientists disagree in their interpretations of what is and is not known. In the current politicized atmosphere, however, legitimate scientific differences about climate change have been lost in the noise of politics.

For some, global warming has become the ultimate symbol of pessimism about the environmental future. Writer Bill McKibben, for example, says, “If we had to pick one problem to obsess about over the next 50 years, we’d do well to make it carbon dioxide.” I believe that we’d be far wiser to obsess about poverty than about carbon dioxide.

Fossil fuels (coal, oil, and natural gas) are the major culprits of the global warming controversy and happen also to be the principal energy sources for both rich and poor countries. Governments of the industrial countries have generally accepted the position, promoted by the IPCC, that humankind’s use of fossil fuels is a major contributor to global warming, and in 1997 they forged an international agreement (the Kyoto Climate Change Protocol) mandating that worldwide fossil fuel use be drastically reduced as a precaution against future warming. In contrast, the developing nations for the most part do not accept global warming as a high-priority issue and, as yet, are not subject to the Kyoto agreement. Thus, the affluent nations and the developing nations have set themselves on a collision course over environmental policy relating to fossil fuel use.

The debate about global warming focuses on carbon dioxide, a gas emitted into the atmosphere when fossil fuels are burned. Environmentalists generally label carbon dioxide as a pollutant; the Sierra Club, for example, in referring to carbon dioxide, states that “we are choking our planet in a cloud of this pollution.” But to introduce the term pollution in this context is misleading because carbon dioxide is neither scientifically nor legally considered a pollutant. Though present in Earth’s atmosphere in small amounts, carbon dioxide plays an essential role in maintaining life and as part of Earth’s temperature control system.

Those who have had the pleasure of an elementary chemistry course will recall that carbon dioxide is one of the two main products of the combustion in air of any fossil fuel, the other being water. These products are generally emitted into the atmosphere, no matter whether the combustion takes place in power plants, household gas stoves and heaters, manufacturing facilities, automobiles, or other sources. The core scientific issue of the global warming debate is the extent to which atmospheric carbon dioxide from fossil fuel burning affects global climate.

When residing in the atmosphere, carbon dioxide and water vapor are called “greenhouse gases,” so named because they trap some of Earth’s heat in the same way that the glass canopy of a greenhouse prevents some of its internal heat from escaping, thereby warming the interior of the greenhouse. By this type of heating, greenhouse gases occurring naturally in the atmosphere perform a critical function. In fact, without greenhouse gases Earth would be too cold, all water on the planet would be frozen, and life as we know it would never have developed. In addition to its role in greenhouse warming, carbon dioxide is essential for plant physiology; without it, all plant life would die.

A number of greenhouse gases other than carbon dioxide and water vapor occur naturally in Earth’s atmosphere and have been there for millennia. What’s new is that during the industrial era, humankind’s burning of fossil fuels has been adding carbon dioxide to the atmospheric mix of greenhouse gases over and above the amounts naturally present. The preindustrial level of 287 parts per million (ppm) of carbon dioxide in the atmosphere has increased almost 30 percent, to 367 ppm (as of 1998).

Few, if any, scientists question the measurements showing that atmospheric carbon dioxide has increased by almost a third. Nor do most scientists question that humans are the cause of most or all of the carbon dioxide increase. Yet the media continually point to these two facts as the major evidence that humans are causing the global warming Earth has recently experienced. The weak link in this argument is that empirical science has not established an unambiguous connection between the carbon dioxide increase and the observed global warming. The real scientific controversy about global warming is not about the presence of additional carbon dioxide in the atmosphere from human activities, which is well established, but about the extent to which that additional carbon dioxide affects climate, now or in the future.

Earth’s climate is constantly changing from natural causes that, for the most part, are not understood. How are we to distinguish the human contribution, which may be very small, from the natural contribution, which may be small or large? Put another way, is the additional carbon dioxide humans are adding to the atmosphere likely to have a measurable effect on global temperature, which is in any case changing continually from natural causes? Or is the temperature effect from the additional carbon dioxide likely to be imperceptible, and therefore unimportant as a practical matter?

Global warming is not something that happened only recently. In Earth’s long history, climate change is the rule rather than the exception, and studies of Earth’s temperature record going back a million years clearly reveal a number of climate cycles—warming and cooling trends. Their causes are multiple—possibly including periodic changes in solar output and variations in Earth’s tilt and orbit—but poorly understood. In recent times, Earth entered a warming period. From thermometer records, we know that the air at Earth’s surface warmed about 0.6ºC over the period from the 1860s to the present. The observed warming, however, does not correlate well with the growth in fossil fuel use during that period. About half of the observed warming took place before 1940, though it was only after 1940 that the amounts of greenhouse gases produced by fossil fuel burning rose rapidly, as a result of the heavy industrial expansions of World War II and the postwar boom (80 percent of the carbon dioxide from human activities was added to the air after 1940).

Surprisingly, from about 1940 until about 1980, during a period of rapid increase in fossil fuel burning, global surface temperatures actually displayed a slight cooling trend rather than an acceleration of the warming trend that would have been expected from greenhouse gases. During the 1970s some scientists even became concerned about the possibility of a new ice age from an extended period of global cooling (a report of the U.S. National Academy of Sciences reflected that concern). Physicist Freeman Dyson notes that “the onset of the next ice age [would be] a far more severe catastrophe than anything associated with warming.”

Earth’s cooling trend did not continue beyond 1980, but neither has there been an unambiguous warming trend. Since 1980, precise temperature measurements have been made in Earth’s atmosphere and on its surface, but the results do not agree. The surface air measurements indicate significant warming (0.25 to 0.4ºC), but the atmospheric measurements show very little, if any, warming.

Briefly, then, the record is this: From 1860 to 1940, Earth’s surface warmed about 0.4ºC. Then Earth’s surface cooled about 0.1ºC in the first four decades after 1940 and warmed about 0.3ºC in the next two. For those two most recent decades, temperature measurements of the atmosphere have also been available, and, while these measurements are subject to significant uncertainty, they indicate that the atmosphere’s temperature has remained essentially unchanged. Thus, the actual temperature record does not support the claims widely found in environmental literature and the media that Earth has been steadily warming over the past century. (A new study that may shed more light on this question—one of a number sure to come—has been circulated but is being revised and has not yet been published.)

For the probable disparity between the surface and atmospheric temperature trends of the past 20 years, several explanations have been offered. The first is that large urban centers create artificial heating zones—“heat islands”—that can contribute to an increase of surface temperature (though one analysis concludes that the heat island effect is too small to explain the discrepancy fully). The second explanation is that soot and dust from volcanic eruptions may have contributed to cooling of the atmosphere by blocking the Sun’s heat (though this cooling should have affected both surface and atmospheric temperatures). In the United States, despite the presence of large urban areas, surface cooling after 1930 far exceeded that of Earth as a whole, and the surface temperature has subsequently warmed only to the level of the 1930s.

It’s frequently claimed that the recent increases in surface temperature are uniquely hazardous to Earth’s ecosystems because of the rapidity with which they are occurring—more than 0.1ºC in a decade. That may be true, but some past climate changes were rapid as well. For example, around 14,700 years ago, temperatures in Greenland apparently jumped 5ºC in less than 20 years—almost three times the warming from greenhouse gases predicted to occur in this entire century by the most pessimistic scientists.

Whatever the current rate of surface warming, there is little justification for the view that Earth’s climate should be unchanging, and that any climate change now occurring must have been caused by humans and should therefore be fixed by humans. In fact, as noted earlier, changing climate patterns and cycles have occurred throughout Earth’s history. For millions of years, ice sheets regularly waxed and waned as global heating and cooling processes took place. During the most recent ice age, some 50,000 years ago, ice sheets covered much of North America, northern Europe, and northern Asia. About 12,000 years ago a warming trend began, signaling the start of an interglacial period that continues to this day. This warm period may have peaked 5,000 to 6,000 years ago, when global ice melting accelerated and global temperatures became higher than today’s. Interglacial periods are thought to persist for about 10,000 years, so the next ice age may be coming soon—that is, in 500 to 1,000 years.

Within the current interglacial period, smaller cyclic patterns have emerged. In the most recent millennium, several cycles occurred during which Earth alternately warmed and cooled. There’s evidence for an unusually warm period over at least parts of the globe from the end of the first millennium to about 1300. A mild climate in the Northern Hemisphere during those centuries probably facilitated the migration of Scandinavian peoples to Greenland and Iceland, as well as their first landing on the North American continent, just after 1000. The settlements in Greenland and Iceland thrived for several hundred years but eventually were abandoned when the climate turned colder, after about 1450. The cold period, which lasted until the late 1800s, is often called the Little Ice Age. Agricultural productivity fell, and the mass exodus to North America of many Europeans is attributed at least in part to catastrophic crop failures such as the potato famine in Ireland.

A plausible interpretation of most or all of the observed surface warming over the past century is that Earth is in the process of coming out of the Little Ice Age cold cycle that began 600 years ago. The current warming trend could last for centuries, until the expected arrival of the next ice age, or it could be punctuated by transient warm and cold periods, as were experienced in the recent millennium.

A great deal of global warming rhetoric gives the impression that science has established beyond doubt that the recent warming is mostly due to human activities. But that has not been established. Though human use of fossil fuels might contribute to global warming in the future, there’s no hard scientific evidence that it is already doing so, and the difficulty of establishing a human contribution by empirical observation is formidable. One would need to detect a very small amount of warming caused by human activity in the presence of a much larger background of naturally occurring climate change—a search for the proverbial needle in a haystack.

Still, understanding climate change is by no means beyond science’s reach, and research is proceeding in several complementary ways. Paleoclimatologists have been probing Earth’s past climatic changes and are uncovering exciting new information about Earth’s climate history going back thousands, and even millions, of years. This paleohistory will help eventually to produce a definitive picture of Earth’s evolving climate, and help in turn to clarify the climate changes we’re experiencing in our own era. But we are far from knowing enough to be able to predict what the future may hold for Earth’s climate.

Mindful of the limited empirical knowledge about climate, some climate scientists have been attempting to understand possible future changes by using computer modeling techniques. By running several scenarios, the modelers obtain a set of theoretical projections of how global temperature might change in the future in response to assumed inputs, governed mainly by the levels of fossil fuel use. But like all computer modeling, even state-of-the-art climate modeling has significant limitations. For example, the current models cannot simulate the natural variability of climate over century-long time periods. A further major shortcoming is that they project only gradual climate change, whereas the most serious impacts of climate change could come about from abrupt changes. (A simple analogy is to the abrupt formation of frost, causing leaf damage and plant death, when the ambient air temperature gradually dips below the freezing point.) Given the shortcomings, policymakers should exercise considerable caution in using current climate models as quantitative indicators of future global warming.

Scientists have long been aware that physical factors other than greenhouse gases can influence atmospheric temperature. Among the most important are aerosols—tiny particles (sulfates, black carbon, organic compounds, and so forth) introduced into the atmosphere by a variety of pollution sources, including automobiles and coal-burning electricity generators, as well as by natural sources such as sea spray and desert dust. Some aerosols, such as black carbon, normally contribute to heating of the atmosphere because they absorb the Sun’s heat (though black carbon aerosols residing at high altitudes can actually cool Earth’s surface because they block the Sun’s rays from getting through to it). Other aerosols, composed of sulfates and organic compounds, cool the atmosphere because they reflect or scatter the Sun’s rays away from Earth. Current evidence indicates that aerosols may be responsible for cooling effects at Earth’s surface and warming effects in Earth’s atmosphere. But the impacts of pollution on Earth’s climate are very uncertain. The factors involved are difficult to simulate, but they must be included in computer models if the models are to be useful indicators of future climate. When climate models are finally able to incorporate the full complexity of pollution effects, especially from aerosols, the projected global temperature change could be either higher or lower than current projections, depending on the chemistry, altitude, and geographic region of the particular aerosols involved. Or, it could even be zero.

In addition to pollution, other physical factors that can influence surface and atmospheric temperature are methane (another greenhouse gas), dust from volcanic activity, and changes in cloud cover, ocean circulation patterns, air-sea interactions, and the Sun’s energy output. “The forcings that drive long-term climate change,” concludes James Hansen, one of the pioneers of climate change science, “are not known with an accuracy sufficient to define future climate change. Anthropogenic greenhouse gases, which are well measured, cause a strong positive forcing [warming]. But other, poorly measured, anthropogenic forcings, especially changes of atmospheric aerosols, clouds, and land-use patterns, cause a negative forcing that tends to offset greenhouse warming.” And as if the physical factors were not challenging enough, the inherent complexity of the climate system will always be present to thwart attempts to predict future climate.

In view of climate’s complexity and the limitations of today’s climate simulations, one might expect that pronouncements as to human culpability for climate change would be made with considerable circumspection, especially pronouncements made in the name of the scientific community. So it was disturbing to many scientists that a summary report of the IPCC issued in 1996 contained the assertion that “the balance of evidence suggests a discernible climate change due to human activities.” The latest IPCC report (2001) goes even further, claiming that “there is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities.” But most of this evidence comes from new computer simulations and does not satisfactorily address either the disparity in the empirical temperature record between surface and atmosphere or the large uncertainties in the contributions of aerosols and other factors. A report issued by the National Academy of Sciences in 2001 says this about the model simulations:

Because of the large and still uncertain level of natural variability inherent in the climate record and the uncertainties in the time histories of the various forcing agents (and presumably aerosols), a causal linkage between the buildup of greenhouse gases in the atmosphere and the observed climate changes during the 20th century cannot be unequivocally established. The fact that the magnitude of the observed warming is large in comparison to natural variability as simulated in climate models is suggestive of such a linkage, but it does not constitute proof of one because the model simulations could be deficient in natural variability on the decadal to century time scale.

These IPCC reports have been adopted as the centerpiece of most current popularizations of global warming in the media and in the environmental literature, and their political impact has been enormous. The 1996 report was the principal basis for government climate policy in most industrial countries, including the United States. The IPCC advised in the report that drastic reductions in the burning of fossil fuels would be required to avoid a disastrous global temperature increase. That advice was the driving force behind the adoption in 1997 of the Kyoto protocol to reduce carbon dioxide emissions in the near future.

In its original form, the protocol had many flaws. First, it exempted developing countries, including China, India, and Brazil, from the emission cutbacks; such countries are increasingly dependent on fossil fuels, and their current greenhouse gas emissions already exceed those of the developed countries. Second, it mandated short-term reductions in fossil fuel use to reach the emission targets without regard to the costs of achieving those targets. Forced cutbacks in fossil fuel use could have severe economic consequences for industrial countries (the protocol would require the United States to cut back its fossil fuel combustion by over 30 percent to reach the targeted reduction of carbon dioxide emissions by 2010), and even greater consequences for poor countries should they ultimately agree to be included in the emissions targets. The costs of the cutbacks would have to be paid up front, whereas the assumed benefits would come only many decades later. Third, the fossil fuel cutbacks mandated by the protocol are too small to be effective—averting, by one estimate, only 0.06ºC of global warming by 2050.

The Kyoto protocol was signed in 1997 by many industrial countries, including the United States, but to have legal status, it must be ratified by nations that together account for 55 percent of global greenhouse gas emissions. As of June 2002, the protocol had been ratified by 73 countries, including Japan and all 15 nations of the European Union. These countries are responsible, in all, for only 36 percent of emissions, but the 55 percent requirement may be met by Russia’s expected ratification. Nonetheless, the treaty is unlikely to have real force without ratification by the United States. The Bush administration opposes the treaty, on the grounds of its likely negative economic impact on America, and has thus far not sought Senate ratification. Even the Clinton administration did not seek ratification, despite its having signed the initial protocol, because it was aware that the U.S. Senate had unanimously adopted a resolution rejecting in principle any climate change treaty that does not include meaningful participation by developing countries.

With the United States retaining its lone dissent, 165 nations agreed in November 2001 to a modified version of Kyoto that would ease the task of reducing carbon dioxide emissions by allowing nations to trade their rights to emit carbon dioxide, and by giving nations credit for the expansion of forests and farmland, which soak up carbon dioxide from the atmosphere. A study by economist William Nordhaus in Science magazine (Nov. 9, 2001) finds that a Kyoto treaty modified along these lines would incur substantial costs, bring little progress toward its objective, and, because of the huge fund transfers that would result from the practice of emissions trading, stir political disputes. Nordhaus concludes that participation in the treaty would have cost the United States some $2.3 trillion over the coming decades—more than twice the combined cost to all other participants. It does not require sympathy with overall U.S. climate change policy to understand the nation’s reluctance to be so unequal a partner in the Kyoto enterprise.

Though the political controversy continues, the science has moved away from its earlier narrow focus on carbon dioxide as a predictor of global warming to an increasing realization that the world’s future climate is likely to be determined by a changing mix of complex and countervailing factors, many of which are not under human control and all of which are insufficiently understood. But regardless of the causes, we do know that Earth’s surface has warmed during the past century. Although we don’t know the extent to which it will warm in the future, or whether it will warm at all, we can’t help but ask a couple of critical questions: How much does global warming matter? What would be the consequences if the global average temperature did actually rise during the current century by, say, some 2ºC?

Some environmentalists have predicted dire consequences from the warming, including extremes of weather, the loss of agricultural productivity, a destructive rise in sea level, and the spread of diseases. Activists press for international commitments much stronger than the Kyoto protocol to reduce the combustion of fossil fuels, and they justify the measures as precautionary. Others counter that the social and economic impacts of forced reductions in fossil fuel use would be more serious than the effects of a temperature rise, which could be small, or even beneficial.

Although the debate over human impacts on climate probably won’t be resolved for decades, a case can be made for adopting a less alarmist view of a warmer world. In any event, the warmer world is already here. In the past 2,500 years, global temperatures have varied by more than 3ºC, and some of the changes have been much more abrupt than the gradual changes projected by the IPCC. During all of recorded history, humans have survived and prospered in climate zones far more different from one another than those that might result from the changes in global temperatures now being discussed.

Those who predict agricultural losses from a warmer climate have most likely got it backwards. Warm periods have historically benefited the development of civilization, and cold periods have been detrimental. For example, the Medieval Warm Period, from about 900 to 1300, facilitated the Viking settlement of Iceland and Greenland, whereas the subsequent Little Ice Age led to crop failures, famines, and disease. Even a small temperature increase brings a longer and more frost-free growing season—an advantage for many farmers, especially those in large, cold countries such as Russia and Canada. Agronomists know that the enrichment of atmospheric carbon dioxide stimulates plant growth and development in greenhouses; such enrichment at the global level might be expected to increase vegetative and biological productivity and water-use efficiency. Studies of the issue from an economic perspective have reached the same conclusion: that moderate global warming would most likely produce net economic benefits, especially for the agriculture and forestry sectors. Of course, such projections are subject to great uncertainty and cannot exclude the possibility that unexpected negative impacts would occur.

As for the concern that warmer temperatures would spread insect-borne diseases such as malaria, dengue fever, and yellow fever, there’s no solid evidence to support it. Although the spread of disease is a complex matter, the main carriers of these diseases—which were common in North America, western Europe, and Russia during the 19th century, when the world was colder than it is today—are most likely humans traveling the globe and insects traveling with people and goods. The strongest ally against future disease is surely not a cold climate but concerted improvement in regional insect control, water quality, and public health. As poverty recedes and people’s living conditions improve in the developing world, the level of disease, and its spread, can be expected to decrease. Paul Reiter, a specialist in insect-borne diseases, puts it this way:

Insect-borne diseases are not diseases of climate but of poverty. Whatever the climate, developing countries will remain at risk until they acquire window screens, air conditioning, modern medicine, and other amenities most Americans take for granted. As a matter of social policy, the best precaution is to improve living standards in general and health infrastructures in particular.

One of the direst (and most highly publicized) predictions of global warming theorists is that greenhouse gas warming will cause sea level to rise and that, as a result, many oceanic islands and lowland areas, such as Bangladesh, may be submerged. But in fact, sea level—which once was low enough to expose a land bridge between Siberia and Alaska—is rising now, and has been rising for thousands of years. Recent analyses suggest that sea level rose at a rate of about one to two centimeters per century (0.4 to 0.8 inch) over the past 3,000 years. Some studies have interpreted direct sea-level measurements made throughout the 20th century to show that the level is now rising at a much faster rate, about 10 to 25 centimeters per century (4 to 10 inches), but other studies conclude that the rate is much lower than that. To whatever extent sea-level rise may have accelerated, the change is thought to have taken place before the period of industrialization.

Before considering whether the ongoing sea-level rise has anything to do with human use of fossil fuels, let’s examine what science has to say about how global temperature change may relate to sea-level change. The matter is more complicated than it first appears. Water expands as it warms, which would contribute to rising sea level. But warming increases the evaporation of ocean water, which could increase the snowfall on the Arctic and Antarctic ice sheets, remove water from the ocean, and lower sea level. The relative importance of these two factors is not known.

We do know from studies of the West Antarctic Ice Sheet that it has been melting continuously since the last great ice age, about 20,000 years ago, and that sea level has been rising ever since. Continued melting of the ice sheet until the next ice age may be inevitable, in which case sea level would rise by 15 to 18 feet when the sheet was completely melted. Other mechanisms have been suggested for natural sea-level rise, including tectonic changes in the shape of the ocean basins. The theoretical computer climate models attribute most of the sea-level rise to thermal expansion of the oceans, and thus they predict that further global temperature increase (presumably from human activities) will accelerate the sea-level rise. But because these models cannot deal adequately with the totality of the natural phenomena involved, their predictions about sea-level rise should be viewed skeptically.

The natural causes of sea-level rise are part of Earth’s evolution. They have nothing to do with human activities, and there’s nothing that humans can do about them. Civilization has always adjusted to such changes, just as it has adjusted to earthquakes and other natural phenomena. This is not to say that adjusting to natural changes is not sometimes painful, but if there’s nothing we can do about certain natural phenomena, we do adjust to them, however painfully. Sea-level rise is, most likely, one of those phenomena over which humans have no control.

Some environmentalists claim that weather-related natural disasters have been increasing in frequency and severity, presumably as a result of human-caused global warming, but the record does not support their claims. On the contrary, several recent statistical studies have found that natural disasters—hurricanes, typhoons, tropical storms, floods, blizzards, wildfires, heat waves, and earthquakes—are not on the increase. The costs of losses from natural disasters are indeed rising, to the dismay of insurance companies and government emergency agencies, but that’s because people in affluent societies construct expensive properties in places vulnerable to natural hazards, such as coastlines, steep hills, and forested areas.

Because society has choices, we must ask what the likely effects would be, on the one hand, if people decided to adjust to climate change, regardless of its causes, and, on the other, if governments implemented drastic policies to attempt to lessen the presumed human contribution to the change. From an economic perspective at least, adjusting to the change would almost surely come out ahead. Several analyses have projected that the overall cost of the worst-case consequences of warming would be no more than about a two percent reduction in world output. Given that average per capita income will probably quadruple during the next century, the potential loss seems small indeed. A recent economic study emphasizing adaptation to climate change indicates that in the market economy of the United States the overall impacts of modest global warming are even likely to be beneficial rather than damaging, though the amount of net benefit would be small, about 0.2 percent of the economy. (We need always to keep in mind the statistical uncertainties inherent in such analyses; there are small probabilities that the benefits or costs could turn out to be much greater than or much less than the most probable outcomes.)

In contrast, the economic costs of governmental actions restricting the use of fossil fuels could be large indeed, as suggested by the Nordhaus study cited earlier on the costs of compliance with the Kyoto treaty. One U.S. government study proposed that a cost-effective way of bringing about fossil fuel reductions would be a combination of carbon taxes and international trading in emissions rights. Emissions rights trading was, in fact, included in the modified Kyoto agreement. But such a trading scheme would result in huge income transfers, as rich nations paid poor nations for emissions quotas that the latter would probably not have used anyway—and it’s not reasonable to assume that rich nations would be willing to do this.

Taking into account the large uncertainties in estimating the future growth of the world economy, and the corresponding growth in fossil fuel use, one group of economists puts the costs of greenhouse gas reduction in the neighborhood of one percent of world output, while another group puts it at around five percent of output. The costs would be considerably higher if large reductions were forced upon the global economy over a short time period, or if, as is likely, the most economically efficient schemes to bring about the reductions were not actually employed. Political economists Henry Jacoby, Ronald Prinn, and Richard Schmalensee put the matter bluntly: “It will be nearly impossible to slow climate warming appreciably without condemning much of the world to poverty, unless energy sources that emit little or no carbon dioxide become competitive with conventional fossil fuels.”

Some global warming has been under way for more than a century, at least partly from natural causes, and the world has been adjusting to it as it did to earlier climate changes. If human activity is finally judged to be adding to the natural warming, the amount of the addition is probably small, and society can adjust to that as well, at relatively low cost or even net benefit. But the industrial nations are not likely to carry out inefficient, Kyoto-type mandated reductions in fossil fuel use on the basis of so incomplete a scientific foundation as currently exists. The costs of so doing could well exceed the potential benefits. Far more effective would be policies and actions by the industrial countries to accelerate the development, in the near term, of technologies that utilize fossil fuels (and all resources) more efficiently and, in the longer term, of technologies that do not require the use of fossil fuels.

If climate science is to have any credibility in the future, its pursuit must be kept separate from global politics. The affluent nations should support research programs that improve the theoretical understanding of climate change, build an empirical database about factors that influence long-term climate change, and increase our understanding of short-term weather dynamics. Such research is fundamental to the greenhouse gas issue. But its rewards may be greater still, for it will also improve our ability to cope with extreme weather events such as hurricanes, tornadoes, and floods, whatever their causes.

Jack M. Hollander is professor emeritus of energy and resources at the University of California, Berkeley. His many books include The Energy-Environment Connection (1992) and The Real Environmental Crisis: Why Poverty, Not Affluence, Is the World’s Number One Enemy (2003), published by the University of California Press, from which this essay has been adapted. Copyright © 2003 by the Regents of the University of California.

p>Do Models Underestimate the Solar Contribution to Recent Climate Change?

Interesting Abstract statement:

"It is found that current climate models underestimate the observed climate response to solar forcing over the twentieth century as a whole, indicating that the climate system has a greater sensitivity to solar forcing than do models. The results from this research show that increases in solar irradiance are likely to have had a greater influence on global-mean temperatures in the first half of the twentieth century than the combined effects of changes in anthropogenic forcings. Nevertheless the results confirm previous analyses showing that greenhouse gas increases explain most of the global warming observed in the second half of the twentieth century.

Though it would be nice to see the results expressed in numbers perhaps you may provide us with that information.

As a quick and dirty linear regression shows, over 70% of the change in temperature since 1850's has been directly correlated with change in solar activity. Less than 15% can be attributed to increasing CO2 (natural plus anthropogenic) concentrations. The substantive remainder variability being short term cyclical fluctions (e.g. elNino etc) and spordic volcanic events.

Of interest is that we passed through a peak in solar activity over the last 50 years in which little has changed in overall activity related to the >80yr Gleisberg cycle.

50 years of unusual solar activity
October 21, 2003
http://physics.about.com/b/a/036554.htm

A moderate (0.0266^oC/decade) linear trend in temperature appears to be detectable which could be corelated with an apparent exponential increase in CO2 concentration. The CO2 correlated trend in temperature is linear because the radiative forcing forcing of CO2 is a logrithmic function of CO2 concentration.

The following global temperature reconstruction is composed of the sum of the relative contributions of Solar & CO₂ concentration as components of temperature.

The Solar Component(S) is the the solution of a linear regression of Solar Activity as measured by Lean '98 for (1956-1977) scaled and appended to the composite ACRIM Satellite data series (1978-2000) of total solar irradiance Frohlich and Lean '98 vs global instumental land & ocean temperatures, Jones et.al '01.

T_s = 0.2685*S-366.95;
Stderror 0.17^oC,
Correlation (R) 0.722

The CO₂ component is the linear regression solution of the natural log of CO₂ concentration from Law Dome ice core data serie(1865-1978) scaled and appended to Mauna Loa Atmospheric CO2 record (1979-2000) vs the residual of the global intrumental temperature series minus the Solar Component above.

T_c=0.6318*ln(CO₂)-3.6324;
Stderror 0.17^oC,
Correlation (R) 0.25

Global Temperature Anomaly, ^oC
Instrumental Global Temperature(T), Jones et al. '01 (black solid line)
Reconstructed temperature (T_s + T_c) from linear regression components(red solid line)

CO₂ + Solar Temperature Anomaly Reconstruction, ^oC
CO₂ contribution to temperature (blue area)
Solar contribution to temperature anomaly (red area)

Note the relative contributions of Solar as compared to CO2 the last 50 years. Solar appears to be peaking out in its Gleisberg cycle while CO2 related factors appear to have established a small linear trend in temperature, at least so long as the exponential rise in concentration is maintained (not a very tenable long term projection).

Of more concern long term is a potential secular trend underlying Solar Activity that has been extracted from the ACRIM 1,2, & 3 satellite data:

Researcher Finds Solar Trend That Can Warm Climate
http://www.earthinstitute.columbia.edu/news/2003/story03-20-03.html

In this study, Willson, who is also Principal Investigator of the ACRIM experiments, compiled a TSI record of over 24 years by carefully piecing together the overlapping records. In order to construct a long-term dataset, Willson needed to bridge a two-year gap (1989-1991) between ACRIM1 and ACRIM2. Both the Nimbus7/ERB and ERBS measurements overlapped the ACRIM ‘gap.’ Using Nimbus7/ERB results produced a 0.05 percent per decade upward trend between solar minima, while ERBS results produced no trend. Until this study, the cause of this difference, and hence the validity of the TSI trend, was uncertain. Now, Willson has identified specific errors in the ERBS data responsible for the difference. The accurate long-term dataset therefore shows a significant positive trend (.05 percent per decade) in TSI between the solar minima of solar cycles 21 to 23 (1978 to present).

That "0.05 percent per decade" may not sound like much but over a centuries time that amounts to (.005*1367*0.7/4) 1.2wm-2 at 0.85oC/w climate sensitivity the IPCC modelers are telling everyone is out their, that is a full 1^oC to look forward to due to the sun alone with around 0.3^oC from exponential increase in CO2 concentrations.

Sure looks like that global warming of at least 1.0^oC + short term variations no matter what and an extra 0.3^oC if we don't manage to run out of exponentially increasing amounts of fossil fuel to burn over the next 100 years.

But wait +1.3 ^oC? Hmmm that puts us back some few thousand years ago.

Somehow I fail to be terribly worried about being able to raise grapes in greenland again. Especially looking at the patterns of past climate cycles of the Quaternary in which we find ourselves and that our progenitors had to go through:

I'll do my best on the Stott, Jones, and Mitchell paper. Feel free to ask questions; this is an important paper, and consideration of it will go a long way toward resolving some of the many questions, accompanied by data, that you have posted. (By the way, I think you REALLY need to get a copy of this paper for yourself. Here's the email of the corresponding author: "peter.stott@metoffice.com" Ask for a reprint or the PDF emailed to you as an attachment.)

In any case; Introduction summarizs work to date, quite well. Discusses solar irradiance measurements. Lean estimates 2 W m-2 increase in solar irradiance between 1900-1950, largest sustained period of increase since Maunder Minimum. Cites all reconstructions (Lean; Hoyt and Schatten (HS); Solanki and Fligge). Discusses amplification mechanisms for solar forcing. Discusses Tett et al. 2002; "no evidence found that the model systematically underestimated the observed climatic response". In all cases, the "model" is the Hadley Centre Coupled Ocean-Atmosphere GCM (HadCM3).

Outlines method: they amplified solar and volcanic forcing and made a single simulation for each forcing.

Section 2 is entitled "Natural contributions to twentieth -century temperature change". Several simulations will be considered: GHG (4 runs, historical chgs in well-mixed GHGs). ANTHRO (4 runs, GHGs + sulfur emissions + effects on clouds + ozone chgs). NATURAL (4 runs, with chgs in stratospheric aerosol due to volcanoes and changes in solar irradiance, based on Lean 1995a. ALL (4 runs with include forcings in both ANTHRO and NATURAL).

This is followed by math and methodology. I can't really summarize. One result is that the warming signal from reduction in volcanic aerosol in the first half of the century is 0.1 K, cooling due to Agung + El Chichon + Pinatubo is 0.25 K, with estimated GHG warming of 1K over the 20th century.

Next: looking at possible underestimation of response to solar or volcanic forcing. Made three further HADCM3 simulations with enhanced forcings to get a clear signal of climate response. Simulations are:

10xLBB: Forced essentially by Lean et al. reconstruction.

10XHS: Forced by Hoyt and Schatten reconstruction (enhanced in the same way as 10xLBB).

5xVOL (forced by volcanic aerosol changes)

10xHS shows two distinct warming periods with cooler periods in 60s and 70s; 10xLBB shows more gradual/consistent warming trend through century. 5xVOL shows expected influences of Krakatoa, low volcanism 1920-1960, then Agung/Chichon/Pinatubo. Notes differences between HS and Lean reconstructions.

Next section is a "test for linearity". Next section is "decadal-mean attribution analysis", mainly an evaluation of scaling factors.

Next section is the "5-yr mean attribution analysis". Conclusion is that with whatever reconstruction is used, "the large-scale temperature response to changes in solar output appears to be underestimated by the model". This is consistent with other detection studies.

Next section is "Reconstructed anthropogenic and natural contributions to observed temperature changes". General warming trend through century due to GHGs; sulfate cooling important mid-century; volcanoes "relatively minor role" but detectable.

Analysis indicates that solar forcing is "likely to be proportionately more important in the first half than the second half of the twentieth century". In first half, solar warming is 0.29 K century, GHGs 0.27 K century.

In first half, HS reconstruction indicates 60% of warming due to solar, Lean 40%. Second half, GHG warming is 2.75x solar for HS, 6.35x solar for Lean. Over entire century, solar accounts for 16% of warming based on Lean, 36% of warming based on HS. [Those are important results.]

Next part discusses scaling factor differences, simulation comparisons. Interesting statement: "... it seems likely that our methodology erroneously overestimates the solar component and underestimates the greenhouse component of observed warming, as a result of the degeneracy between the patterns of response to these two forcings."

Very vital start to the next paragraph: "Amplifying the solar signal, in combination with the anthropogenic and volcanic signals, produces an improved fit to the observed large-scale temperature evolution during the twentieth century. Global warming observed over the past three decades is well reproduced in the ANTHRO ensemble alone, but the addition of an enhanced solar contribution improves the fit to early century warming." Then discusses some observed regional discrepancies.

Summary and discussion section: Most important conclusions have already been covered above. Noteworthy sentences:

1. "Our results imply that solar forcing had a greater impact on near-surface temperatures than simulated by HADCM3, and that previous attribution analyses may have underestimated the potential contribution of solar forcing to twentieth- century global warming." (Climatic processes could amplify surface temperature response by 1.34x-4.21x for LBB, 0.70x to 3.32x for HS).

Summarizing next paragraph, not quoting: Even with enhanced climate response to solar forcing, warming over last 50 years caused by increasing GHGs. GHGs probably caused more warming than observed, as some cooling was due to sulfate aerosols. Warming from solar forcing est. 16-36% of warming due to GHGs.

Next section prognosticates the future a bit; I'll skip that for now; I can summarize it subsequently if you're interested.

Final paragraph, interesting sentence: "Although our study indicates that there could be an enhanced global-scale temperature response to solar forcing, convincing evidence for a mechanism remains elusive." Mentions UV-ozone connection and possible changes to planetary waves and Hadley circulation; also mentions cosmic ray-cloud (or electrical!?) connections.

That should get you thinking; I should be able to continue next week with obvious interruptions expected.

I'll be going out for a good portion of the rest of today so I might not be able to respond quickly after this reply. To let you know where I am going with this the following is a general description of the methodology I am using to extract the solar related components of instrumental temperature for comparison with non-solar related CO2 and residuals such as el-nino and lesser effects.

There are a couple of things that are coming out of my own Principal Component Analysis, removing cross correlations between terms accumulates the direct and indirect forcings under each principal term.

The essence of the method aggregates the total effects of "Principal Components" into singular terms of a linear series.

Basically one starts with an component having the highest correlation with the subject signal, extract that signal from all other components under investigation, then goes to the component having the next lower correlation doing the same in turn. The object is to develop a series of varibles that are minimally correlated between each other from which an index may be developed to reflect the subject data series to be simulated.

Principle Component Analysis
http://goanna.cs.rmit.edu.au/~santhas/research/paper2/node9.html

Principle component analysis is one of the simplest multi-variate methods that can be useful in analyzing data sets involving high-dimension feature vectors. The object of the analysis is to take n-dimensional vectors (represented by n variables, X₁, X₂, ... X_n) and find combinations of these to produce indices Z₁, Z₂, ... Z_n that are uncorrelated. The lack of correlation is a useful property because it means that the indices are measuring different ``Hypothetical dimensions" of data. However, the indices are also ordered so that, Z₁ displays the largest amount of variation, Z₂ displays the second largest amount and so on. When doing a principle components analysis, there is always the hope that the variances of most of the indices will be so low as to be negligible. In that case the variation in the data set can be adequately described by the first few Z's with the variances that are not negligible. The best results are obtained when the original variables are highly correlated. If that is the case, then it is quite conceivable that 20 or 30 dimensions can be adequately represented by two or three principle components.
The i^th principle component is defined as;
Z_i = a_i1X₁ + a_i2X₂ + ... + a_inX_n
where a_ij are the coefficients of the i^th eigen vector of the corresponding correlation matrix.

While I do not have a matrix oriented spreadsheet available to me, it is not too difficult to adapt standard linear regression techiques to accomplish the same results when only looking at small number of independant variables for the index under study.

The magnitudes of the results I am achieving are giving somewhat stronger results for solar influence and lesser role for non-solar related CO2 concentrations than the studies you summarize above.

I suspect the basic difference being the PCA technique does not attempt to emulate a multiplication of the a particular level of forcing i.e. 2wm^-2 of say Solar Activity by an atmospheric component such as water vapor. PCA merely fits the independant component to the observed data thus incorporating any "climate senstitivity" to component forcing into the resulting coefficient.

Since the method removes any cross correlation from succeeding components to create independant variables, each term becomes unique and truly independant of all others each with primary forcing and related multiplies incorporated into the term coefficient.

The particlular series I am working with essentially works out to look something like:

T = aS + bX +R

Where

S = the solar component index,
X = CO₂ component index, [ln(CO2)] less any Solar correlation.
R = Uncorrelated residual from the linear regression of S & X with respect to the Subject temperature series T.

First pass indicates the order of the terms to be Solar first, CO2 takes the secondary position as a consequence of lower correlation with temperature as well as Solar activity having a positive strong causitive relation on CO2 concentration both from direct measurement and theoretical considerations. There is simply no avenue for earth based CO2 to have an effect on the measures of Solar activity (principally observations of sunspot count etc.)

Initial pass puts the 11 yr averaged Solar index alone in primary position with a correlation of >0.76 with respect to the Jones '98 instumental series.

The logrithm of raw CO2 concentration alone has a lesser correlation with respect to the Jones '98 instumental series.

CO2 is cross correlated with the Solar index by >0.82 requiring the removal of the solar related component from it before using it as a term in the index series.

That just means the the raw CO2 component has a strong dependency on solar factors. Not a tremendous surprise as one source of CO2 is from solar heating of the oceans causing an immediate rise in atmospheric CO2 concetrations as solar activity increases. Thus the Solar faction of CO2 concentrations must be removed from the raw CO2 term to meet the conditions of uncorrelated variables that define the Principal Component Analysis.

The CO2 term ends up having only geophysical(mainly volcanic) and biomass decay components(delayed solar relationships) and anthropogenic(fossil fuel consumption etc.) related concentrations while immediate solar related concentrations are removed.

Anyway, when I complete the necessary speadsheet and can pull out a numeric & graphical result to display the index , I'll be sure to pass it on to you ;O)

Looking over the summary you provided, my primary remark remains the same as I make concerming the inadequacy of the GCM's in general. They are not designed to adequately model the processes of solar variations and thus overstate the contributions of GHGs.

The study is fine, its primary result being to test the response of a Model to a set of solar forcings.

In using the Lean data to test the sensitivity of a "Model" to solar forcings, Lean is one of the most concervative of the solar forcings that can be used. The Lean data is scaled on the assumption that the Maunder Mininmum was the result of no more than a 0.25% change in solar activity. Thus the 2wm^-2 variation applied as forcing in the GCM. However, other studies estimate the variation in solar forcing to be substantially larger than that Lean(no pun intended ;o) 0.25% estimate.

ftp://ftp.ngdc.noaa.gov/paleo/climate_forcing/solar_variability/bard_irradiance.txt

2. Data from Figure 3. Reconstructed Solar Irradiance Scaled against Maunder Minimum Total Solar Irradiance reductions of

0.25% (Lean et al. 1995),
0.40% (Zhang et al. 1994, Solanki and Fligge, 1998)
0.55% (Cliver et al. 1998), and
0.65% (Reid 1997)

Using Zang, Solanki & Fligge, Cliver, or Reid the Solar forcing introduced into the GCM tested would have caused a substantially greater Solar response greatly reducing the CO2 contributions necessary to reflect historical instrumental record.

That is what PCA and Linear Regressions of Solar activity are showing and what a model that focuses on greenhouse effect with built in presumptions favoring GHG processes cannot adequately reflect.

A model can only reflect the apriori postulates of its programmers. If any physical processes are not adequately characterized in a model, all outputs are in question.

Essentially what the Stott, Jones, and Mitchell paper appears to achieve is test a particular climate model against a couple of the more conservative solar irradiance series available and declares it inadequate as regard solar forcing responses.

Conclusion is that with whatever reconstruction is used, "the large-scale temperature response to changes in solar output appears to be underestimated by the model". This is consistent with other detection studies."

That being the case, no conclusions can be drawn from that model as regards the accuracy of how it reflects real world processes. The model tested in the study must be viewed as inaccurate as a consequence of inadequate treatment of solar forcings. Thus one must conclude, because the GCM underestimates the response to solar forcings,the GCM must give excessive weight to minority GHG's to achieve an apparent fit to instrumental measurements.

In my view, I cannot accept the GCM's configured by the UN/IPCC teams as being much more than over characterised polynomials and incapable of anything more than interpolation between known global temperature data points. The individual components making up those interpolaters do not accurately reflect the response of true physical processes and thus are incapable of making accurate projections outside the range of the dataset it is fitted to.

The GCMs appear to make the mistake of adding terms to what has become little more than an ultra fancy polynomial regression forced to fit historical data by adding compensating arbitrary terms rather than emulating measured physical processes with known inputs. Works great as an interpolator between known data points, but don't expect anything reflecting reality outside the range of the fitted dataset.

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